Control of Phytophthora nicotianae of Tomato by Using Non-Conventional Strategies

Phytophthora nicotianae is a common and destructive pathogen of tomato. In Italy, P. nicotianae is observed as a common pathogen of tomato in protected crops and is an emerging problem on tomato grafted on rootstocks belonging to Solanum lycopersicum x S. hirsutum. Alternative strategies for disease control are needed. This work was carried out in order to test preventative treatments based on the use of biocontrol agents, compounds known for their capability of inducing resistance to several pathogens in plants, phosphite-based fertilizers, organic amendments based on Brassica carinata pellet and fungicides to control P. nicotianae under nursery conditions, in greenhouse. The 'Cuore di Bue' tomato seedlings grown in tray were treated by leaf spray treatment at a 6-7-day interval, at least three times with the exception of Brassica carinata pellet, the product based on arbuscular mycorrhizal fungi and microbial complex and fungicides applied once. The first treatment was carried out on tomato plants, still in the plug tray, at the stage of 3-4 true leaves. Among the chemical resistance inducers tested, acibenzolar-S-methyl was highly effective in all trials in controlling Phytophthora crown root rot on tomato at both dosages tested (0.025 and 0.0125 g L-1). The results provided by the tested phosphite-based mineral fertilizers were often statistically similar to those offered by the most active fungicides (metalaxyl-M and azoxystrobin). The only partial results obtained in our study with the application of biological control agents confirmed that, in most cases, biocontrol agents can only play a role when applied within integrated control programmes. B. carinata pellets were ineffective in all trials.